1. Field of the Invention
The invention relates to a method for producing generator gas and activated carbon from solid fuels, as well as to an apparatus for performing the method.
2. Description of the Relevant Art
German Laid-Open Patent No. 33 35 544 discloses a reactor means for producing lean or generator gas from biomasses or other carbonizable by-products. It has a primary gasifier and a series-connected secondary gasifier, to each of which air is supplied. A flue flow gas converter is provided between the primary gasifier and the secondary gasifier. An intermediate gasification takes place in the gas converter. The fuel is supplied proportionally by means of an underfeed charging system, and the gasification air is introduced through a ring nozzle or a central nozzle in a rotationally symmetrical manner. There is a substantial heat return or recycling of hot, exiting generator gases to the gasification air and preheating of the fuel.
It has been found that different fuels, even those with a high water content, can be gasified by the known apparatus in an environmentally safe manner. The apparatus achieves relatively high efficiency levels and solves sewage problems in connection with the tar and phenol contents. However, it has been found that there is a risk of the coal encrusting under the existing fill level sieve or screen in the primary reactor. The known apparatus is used both in the case of small and larger installations, and it has been found that instabilities occur in the primary reactor. The through-flow with air can become one-sided after a few hours' operation and can lead to channelling with subsequent slag formation. Due to the fuel grain size and the specific operating capacity levels, the generator gas in the primary stage contains too much flue coal, which blocks the secondary reactor. There is consequently a fluctuation in the pressure losses, and a large amount of coal must be discharged from the secondary reactor in the form of fine coal, which is not usable, since the secondary reactor requires reactive coke which is coarse-grain and relatively hard. Simultaneously, there are fluctuations in the coke consumption in the secondary reactor. This can lead to high costs under least favorable operating conditions.
German Patent 50 137 describes a gas generator with a combustion chamber to which fresh fuel is supplied from above. Under the fresh fuel layer, there is an ash layer on the bottom plate provided beneath the combustion chamber. The bottom plate can be rotated by means of a crank, so that the ash drops over the edge of the bottom plate into an ashpit. Air and/or steam is passed through the bottom plate into the combustion chamber.
The object of the present invention is to provide a method and an apparatus for producing generator gas and activated carbon from solid fuels, whose operating conditions are constant regardless of the apparatus size. Another object of the present invention is to make it possible to rapidly regulate the individual operating quantities. Yet another object is to provide a method and apparatus which efficiently produces a generator gas with a high purity level.